 Tail pipe inserts |
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| moggy |
 Jul 3 2014, 03:33 AM
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#1
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Member  Group: Members Posts: 192 Joined: 15-December 04 From: Wales Member No.: 3,285  |
Hi guys
What's the significance of the insert inside the end of this tailpipe? (IMG:http://www.914world.com/bbs2/uploads/post-222-1372820267.jpg) I see it a lot on big vintage 911 engines too. Is it there as a noise control solution, breaking up the sound wave in some way? or is there something else going on? |
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| wndsrfr |
Jul 4 2014, 09:18 AM
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#2
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Senior Member Group: Members Posts: 1,428 Joined: 30-April 09 From: Rescue, Virginia Member No.: 10,318 Region Association: MidAtlantic Region 
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QUOTE(moggy @ Jul 3 2014, 01:33 AM)  Hi guys What's the significance of the insert inside the end of this tailpipe? I see it a lot on big vintage 911 engines too. Is it there as a noise control solution, breaking up the sound wave in some way? or is there something else going on? Keeps the competition at bay since it looks like a missle aimed at your nose! (IMG:style_emoticons/default/av-943.gif) |
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| crresind |
Jul 4 2014, 09:51 AM
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#3
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Newbie Group: Members Posts: 13 Joined: 8-June 04 From: Oceanside, California Member No.: 2,175 Region Association: Southern California |
This is called "cookie cutter exhaust". Porsche claimed that this was helpful above 8200 rpm on their race cars. I have found that they take some of the harshness out of open exhaust. This is not an "insert", the megaphone is built this way.
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| campbellcj |
Jul 5 2014, 10:24 AM
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#4
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I can't Re Member Group: Members Posts: 4,543 Joined: 26-December 02 From: Agoura, CA Member No.: 21 Region Association: Southern California
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I thought it was simply to make the pipe stronger...
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| moggy |
Jul 7 2014, 03:43 AM
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#5
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Member Group: Members Posts: 192 Joined: 15-December 04 From: Wales Member No.: 3,285 |
QUOTE(crresind @ Jul 4 2014, 07:51 AM) This is called "cookie cutter exhaust". Porsche claimed that this was helpful above 8200 rpm on their race cars. I have found that they take some of the harshness out of open exhaust. This is not an "insert", the megaphone is built this way. Interesting. Thanks. Although my engine will not see the dizzying heights of 8200rpm, anything to help lower the db is good for me at the moment. |
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| Cap'n Krusty |
Jul 7 2014, 05:50 PM
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#6
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
A long time ago, these were called anti-reversionary tail pipes. Looking the term um on Google, I'm not sure they meed the definition. They were all the rage with the PCA/POC long track guys. The Chief had 'em on his 904/6, Otto on his 914/6, and most of the other fast guys used them. It could be that they were more trendy than effective, just like a lot of car fads. They DO look cool, though ..................
The Cap'n |
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| '73-914kid |
Jul 9 2014, 08:11 AM
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#7
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Senior Member Group: Members Posts: 1,473 Joined: 1-November 08 From: Vista, CA Member No.: 9,714 Region Association: Southern California  |
The story I always heard was that they were to prevent the pipes from getting pinched closed if the car was tapped from behind. Given how far 911 megaphones stick outward from the bumper, it's not a bad idea to have them installed.
BTW, I ran my car with 2 sets of megaphones of the exact dimensions. 1 pair without cookie cutters, and 1 pair with inserts. No difference in sound, power, or anything of that sort. |
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| zymurgist |
Jul 9 2014, 11:32 AM
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#8
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"Ace" Mechanic Group: Members Posts: 7,411 Joined: 9-June 05 From: Hagerstown, MD Member No.: 4,238 Region Association: None |
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| Seabird |
Jul 9 2014, 02:28 PM
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#9
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Member Group: Members Posts: 165 Joined: 21-November 13 From: United States Member No.: 16,683 Region Association: South East States |
QUOTE(zymurgist @ Jul 9 2014, 09:32 AM) Laughed my butt off when that video first hit youtube still laughing now, WoootWooooo! |
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